Bituminous paving material and method of making the same



Patented Mar. 15 1938 PATENT OFFICE BITUMINOUS PAVING MATERIAL AND METHODIOF'MAKING THE S ME 7 Samuel S. Sadtler, Springfield T'ownship,Montgomery County, and Woolsey H. Field, Wyncote, Pa., assignors to Bituvert Corporation, a

corporation of New Jersey No Drawing; Application May 24, 1933, Serial No. 672,737

4 Claims. (01. 1063l) Our invention relates to the coating 'of'various kinds of mineral aggregate withdifierent kinds of bituminous compositions, all with the object of securing a firmpermanent bond between the coating and 1 the aggregate, and the consequent increase in the length of the life of the finished product.

One of the objects of the present invention is to prepare the surfaces of the pieces of aggre-- lO gate with a bituminous film for the reception of the cement or binder by which the mass is firmly held together, but the film itself is so thin and the bitumen forming the film is of so low 'or of so high a penetration that the contacting pieces 15 of aggregate in a mass of aggregate do not cohere, but the mass remains discrete and Waterproofed or water-resisting prior to the application of the binder-cement thereto. v A further object of this invention is to provide amethod of waterproofing mineral aggregates prior to the application of the bituminous binder thereto whereby the stone thus treated will thereafter have a surface to which bituminous binder cements of various kinds have -a strong affinity and over which they readily spread and coat the individual pieces, although the binding cement or finishing coating may be applied long after the aggregate so-pre-coated or pretreated has stood in piles and has been subjected to climatic exposures.

A further object of'this invention is to provide the individual pieces of a graded mineral aggregate with a film of bituminous material of such high or of such low penetrationthat the pieces, in a mass or pile, do not c'ohere and the mass remains discrete.

A further object of this invention is to so: treat a mineral aggregate as to provide it with a surface film or coating for which an adhesive bituminous binder has a natural aflinity and with 40 which it readily unites to form a thick binder coat and which therefore readily lends itself to the practice of what is known as penetration methods of binding pieces of aggregate together, for when the stone has been provided with the bituminous film in accordance with this invention, the penetration cement, when applied to a mass of aggregate, instead of working its way through the aggregate to the bottom of ithe course through separated channels or paths, 5 spreads evenly over the precoated surfaces, with the result that after the penetration cement has been applied, the binding cement is relatively uniformly distributed throughout the course and over the particles or pieces instead of being re-' tained inseparated small pockets and instead of leaving some of the aggregate uncoated with the bindercement.

In the making ofhighways, it becomes often necessary to utilize as the aggregate, stones of different kinds dependent upon the place where the road is being laid. To illustrate what is meant, it is here pointedout that if a bituminous aggregate roadway were being placed in a territory in which limestone abounds, it often becomes necessary and desirable to utilize such relatively soft water-absorbent stone as limestone, as the aggregate upon which the bitumen is to be applied. On the other hand, if the roadway is being placed in a territory in which a harder stone, such as trap rock, is available, then that stone is highly desirable. The object of the invention, therefore, is to provide a method of treating stones which are satisfactory as to strength and wear resistance, such as trap rock, dolomite, limestone, silicates, slags, etc., in pieces of suitable size, and the preliminary treatment to which these materials are subjected may differ in some respects quite substantially.

'Moreover, under some circumstances, it may be possible to use dry aggregate, particularly if the aggregate be water-absorbent, and, on the other hand, it may be highly desirable to use a wet aggregate and to dispense with the expense of expelling the water therefrom, or to dry the surface of the stone. It is an object of this invention to provide a process whereby a bituminous binder cement may be applied to the aggregate after a pre-treatment, whether the stone originally used is Water-absorbent or nonabsorbent, or is wet or dry.

A further object of this invention is to provide a method of .pre-coating or pre-treating a mineral aggregate for the subsequent application thereto of a bituminous binder that the pre-coating may be so easily applied and at so little cost that when done on a large scale the cost of the stone is not substantially increased over an untreated stone and the market for such stone is thereby greatly increased. Such pretreated stone might be used without further treatment in place of uncoated stone, as for the surface sealing of a bituminous concrete paving course where its surface film would be of substantial aid in causing the cement of the main or wearing course to retain the sealing material in place on the roadway.

One of the purposes of the present invention is to provide the surface of the pieces of aggregate with a film of arbituminous nature, the film Further objects of this invention will appear in the specification and claims below.

This invention comprises, in the main the formation of a discrete mass of bitumen coated aggregate, that is to say, a mineral aggregate coated with a thin bituminous film which is permanent, waterproof, not adhesive enough to cause the contacting pieces to cohere at atmospheric temperatures and provides the aggregate with a surface for which a bituminous cement has a natural affinity, so that bituminous cement of such anature and consistency that it binds by cohesion the contacting pieces of coated aggregate into a relatively firm permanent mass at atmospheric temperatures may subsequently be added thereto. Since the pro-coating of the aggregate may be performed in several different ways, and since the pre-coated aggregate maybe utilized without further treatment for certain, purposes, various ways of pre-coating the aggregate will be described, it being understood that the actual quantity of bitumen used may vary with aggregates graded to different sizes.

In many cases the stone which is to be used, whether hard or water absorbent, is wet and facilitates for drying the same may or may not be available. The present process, therefore, contemplates the use of wet aggregate and the elimination of the drying step. This, dampness may be the result of exposure to the. weather or it may be due to the washing of the aggregate, or to the fact that the stone coming from the quarry is damp. In such cases, after the batch of graded aggregate has been placed in the mixing apparatus from one-half to one pound of ordinary soap, preferably in chips, or other comminuted form, is added to the aggregate under agitation. With large aggregate less soap will be needed than with finer or smaller aggregate, such as is ordinarily used for top courses of pavements, and chips or fines for surfacing bituminous pavements. After the soap thus added has been dissolved in the water a relatively small quantity of any of the bituminous high penetration substantially fluid coating materials is slowly added to effect a substantial emulsification of the latter. In this manner a good bondage of the oil or other bituminous material to the aggregate is effected. Bunker C fuel oil is satisfactory for the purpose.

After the oil has been added and while the agitation is being continued, a small percentage of the asphalt, which may have a penetration between substantially 4 and substantially 50, is added and thoroughly mixed into the batch. After this asphalt has thus been thoroughly distributed over the surfaces of the pieces of aggregate, a small quantity of aluminum sulphate, or a solution of the same, is added to the mixture under treatment.

The weight of the aluminum sulphate so added is preferably substantially one-half the weight of the soap employed in the mix. The aluminum sulphate forms aluminum compounds of the fatty acids of the soapand neutralizes the soap.

The formation of aluminum salts of organic acids in this manner is so desirable that in carrying out this process in this modification it is preferred to use damp stone, and, if the stone be dry, a little water may be added tothe stone directly or with the soap, so as to form the emulsion above described and the bitumen to make a firm contact with the aggregate.

We may however use an asphalt of higher penetration which asphalt may be an ordinary asphalt, in excess of 50 penetration and of the order of 9 penetration, or other bitumen. If the aggregate is very water absorptive and undried it is generally necessary to drive out the water at some stage before using the precoated aggregate. This may be effected by storing the material under cover or expelling the water by means of a rotary drier until the oily portion of the coating material has penetrated sufficiently to protect the aggregate against further water attack.

In some cases it may be desirable to provide the aggregate with the film of an already prepared emulsion of a bitumen. As an example of this manner of practising this invention, we emulsify in any of the well known Ways, as in an emulsifier, substantially 100 pounds of a 50 penetration asphalt using substantially gallons of water, 3 gallons of naphtha and 2 pounds of ordinary soap. The emulsion having been formed in any of the ordinary well known apparatuses, a sufficient quantity of this emulsion is added to the stone in a mixing machine to form a film on the aggregate, after the water and the naph tha have been evaporated. The weight of bitumen employed is preferably not more than substantially 0.3% of the weight of the mixture when the aggregate is large, and about 1.0% of the completed mixture for small sized aggregate.

After the emulsion has been thoroughly distributed over the pieces of stone by agitation and while the agitation is being continued a small amount of aluminum sulphate, in quantity substantially one-half the weight of the soap, is added to throw the bituminous material out of suspension in the soapy water, and to form aluminum salts of the organic acids of the soap to neutralize the soap ashas been previously referred to.

By the above described modes of treating different kinds of stone, under different conditions as to the presence of water, there is obtained a product comprising an aggregate, each piece of which is provided with a coating, film-like in character, completely enveloping each piece and protecting it, by virtue of its firm adherence thereto, from deleterious effects of exposure to atmosphere, the said film being operative to keep the aggregate in a condition in which a bituminous cement may be thereafter applied thereto, to produce, from the discrete non-cohesive pieces a material which will form a solid course of pavement upon the application theretov of a suitable bituminous cement and the placement of said cement-coated aggregate on the highway. This product also particularly lends itself to use in connection with the patching of bituminous roadways, for the pre-coated aggregate may be left for considerable periods of time in piles or heaps along the. roadway and when needed for patch work, is ready for admixture with a suitable bituminous cement on mixer boards or in portable mixers or by penetration without further preparatory treatment.

A pro-coated fine aggregate, without further treatment, may be spread over the surfaces of newly constructed bituminous concrete pavements for the purpose of eifectively sealing the surface course from the entrance of water, for such pre-coated small pieces readily and permanently adhere to the aggregate forming the surfaces of the road and covered with a bitumi nous cement because of the afiinity between the film on the fines and the bituminous cement of the course on which they are laid.

And this pre-coated material is also useful for other purposes. Thus posts and poles may be set by first putting the pole or post in a hole dug in the ground and then filling the hole around the post with pre-coated mineral aggregate of the proper size and grade and then binding the pieces of pre-coated aggregate together by pouring a bituminous cement liquefied by heat, or a hard asphalt or other bitumen cut-back with a solvent over the surface of the aggregate so placed around the pole or post. The surface of the pre-coated aggregate is one for which the cement has an afiinity. The cement substantially flows over and covers the pieces providing them with a thick even coating of cement and firmly binding the pieces together in a solid The cement does not behave as it does when the aggregate is not thus provided with the bituminous film, and wherein the fluid cement follows the easiest course in separated streams through the mass from void to void without covering the surfaces of the pieces of aggregate. It is for this reason that the pre-coated aggregate also particularly lends itself to the making of penetration pavements as will be referred to below.

It will now be more apparent that one of the aspects of this invention embodies the easy preparation of an aggregate having a film of bituminous material completely covering and protecting the same and that this may be so cheaply applied to the stone, that it may be done on a a large scale at the place where the stone is quarried and crushed and may be distributed as a graded coated mineral aggregate in a discrete mass, for the application thereto of a thick surface coating of a bituminous cement, and for various uses.

The quantity of bituminous material applied to the aggregate in accordance with the present invention is relatively small because of the very thin film which is provided, and for a coated aggregate will ordinarily lie in the range from 0.3% to 1.0% of the weight of the aggregate, and not in excess of 1.2% by weight, dependent, of course, upon the character, size and condition of the aggregate.

Having thus disclosed a variety of ways in which the present invention may be practiced with various materials and. ingredients, it is to be understood that the invention is not to be construed as limited to the exact formulae or exact proportions of ingredients, the formulae being by way of example and illustrative of the best ways known by these applicants of making and using the invention. Unless so expressly limited, the claims are to be construed broadly.

Having thus described our invention, what we claim and desire to protect by Letters Patent of the United States is:

1. A paving material consisting of graded pieces of mineral aggregate, each piece being provided with a bituminous coating completely covering the entire surface of each piece of aggregate as a bituminous film, and bitumen being of low penetration, and firm and the coating so thin, so that the coated pieces do not cohere, and a mass of said pieces is practically discrete, said bituminous material containing a small quantity of a water-insoluble metallic salt of an organic acid, the quantity of the bituminous material on the aggregate being from 0.3% to 1.2% of the weight of the coated aggregate, depending upon the size of the aggregate. 2. A paving material consisting of pieces of graded mineral aggregate each having a bituminous coating completely covering the entire surface of each piece of aggregate with a bituminous film of relatively low penetration bitumen, said bitumen being firm and the coating very thin so that the coated pieces do not where, and a mass of said pieces remains discrete over long periods of time, said bituminous material containing less than 3% of an aluminum salt of an organic acid, the quantity of the bituminous material on the aggregate being from 0.3% to 1.2% of the weight of the coated aggregate, depending upon the size of the aggregate.

3. The method of providing a damp mineral aggregate with a film of bituminous material which consists in agitating said damp aggregatein the presence of soap until the soap has dissolved, then adding a bitumen solvent, bitumen and finally an aluminum salt, the quantities of said materials for a ton of a finished mixture being substantially:

Mineral aggregate pounds 1984 to 1968 Soap 1 pounds to 1 Naphtha gallons 1 to 2 Asphalt cut back to moderate fluidity with naphtha pounds 25 to 30 Powdered aluminum sulphate pounds A to A Pounds Wet mineral aggregate, about 1980 Heavy oil 6 to 12 About penetration asphalt 6 to 12 Soap /2 to 1 Aluminum sulphate A to 1 SAMUEL S. SADTLER. WOOLSEY H. FIELD. 

